1. Field of the Invention
The present invention relates to a swallowing test apparatus which tests the swallowing movement of a biological body (movement that transfers a bolus of food, which is an object to be swallowed, from the oral cavity to the stomach).
2. Description of the Related Art
Dysphagia is caused, for example, by deterioration of physical ability associated with aging or by stroke or cerebral neurological disorder such as Parkinson's disease. A large number of patients are suffered from dysphagia in developed countries including Japan where the aging population is increasing. Patients with dysphagia sometimes misswallow a bolus of food into the bronchial tubes (air passage) or the lung, which may cause pneumonia, leading to high fever. Therefore, when aged people who are short on physical strength are suffered from dysphagia, they are exposed to dangers in which they may lose their life.
As the method for evaluating and determining dysphagia correctly, a VF method (i.e. Videofluoroscopic Examination of Swallowing) is the most common method. In the VF method, an X-ray machine for recording the swallowing movement is used to monitor a bolus of food including contrast media such as barium sulfate that a subject has swallowed. Because the swallowing movement is a series of quick movements, it is common to capture the swallowing movement on video for evaluation. However, the VF method requires extra caution because it has a risk that the subject may misswallow the bolus of food or be suffocated. Moreover, because the VF method uses an X-ray machine, there have been problems of exposure to nuclear radiation, a prolonged test time and costs related to the X-ray machine.
Another method recently introduced is a method for evaluating dysphagia by using a fiberscope. This method is called a Videoendoscopic Examination of Swallowing (VE). The VE method has advantages over the VF method in that a test for dysphagia is carried out easily bringing a fiberscope to a bedside of a patient, and the states of the mucous membranes or tissues of the pharynx and the larynx or saliva retention can be evaluated. However, the VE method also has disadvantages that subjects feel uncomfortable when a fiber is inserted through their nasal cavity, and because a fiberscope apparatus is necessary, a test for dysphagia is still not simple. Thus, the VE method has not been prevailed. Furthermore, the VE method also has a problem that when a bolus of food is transferred into the pharynx, the wall of the pharynx is closed and the space in the pharynx becomes smaller, the view through the fiberscope becomes obscure, and thus the swallowing movement can not be monitored in the time zone in which the organs related to the swallowing movement moves at most in a short time. The time zone is refereed to as “white out”, and indicates the limitation of the VE method.
As a method for solving the above problems in the VF method and the VE method, JP Unexamined Patent Publication (Kokai) No. 2005-304890 discloses a method for simply identifying dysphagia correctly without imposing a burden on a patient. In the method disclosed in JP Unexamined Patent Publication (Kokai) No. 2005-304890, electrodes are arranged on a plurality of muscle surfaces concerned with swallowing to record a surface electromyogram, a microphone for recording a swallowing sound is disposed and an acceleration sensor is used for recording the vibration of the throat at the time of the larynx elevation. In the method, patterns of data obtained are learned by neural networks so that dysphagia can be identified.
The method disclosed in JP Unexamined Patent Publication (Kokai) No. 2005-304890, however, has disadvantages that data obtained by the electromyogram, the swallowing sound and the acceleration sensor has to be organized into database and patterns of the data has to be learned by neural networks in order to identify dysphagia, which is time consuming and troublesome. Furthermore, JP Unexamined Patent Publication (Kokai) No. 2005-304890 does not disclose how to differentiate a subject with dysphagia and a healthy subject, and thus it is difficult to use the method in practice. Moreover, in the method, patterns of each kind of data are learned individually without considering relationships of each kind of data, and only a result of a process determining whether or not a subject has dysphagia is output. Thus, the degree of dysphagia can not be represented visually. As described above, JP Unexamined Patent Publication (Kokai) No. 2005-304890 does not disclose techniques of comparing the waveforms of each kind of data, directly determining the degree of dysphagia based on the waveforms of each kind of data, and determining the degree of dysphagia easily. Thus, the method disclosed in the JP Unexamined Patent Publication (Kokai) No. 2005-304890 is poor at visual representation, and it is difficult to determine the degree of dysphagia clinically.
In Non-patent article 1 and JP Unexamined Patent Publication (Kokai) No. 2006-95264, a swallowing motion measuring system is disclosed which uses pressure sensors (for detecting larynx movement), a surface electromyogram and a vibration pickup (for detecting a swallowing sound). Similarly to the method disclosed in JP Unexamined Patent Publication (Kokai) No. 2005-304890, however, the method disclosed in non-patent article 1 evaluates parameters of each kind of data (the value of electromyogram, the time when the output of the pressure sensor is at the maximum, an average cycle and swallowing sound power) independently. Thus, non-patent article 1 also does not disclose techniques of comparing the waveforms of each kind of data, directly determining the degree of dysphagia based on the waveforms of each kind of data, and determining the degree of dysphagia easily. Therefore, the method disclosed in non-patent article 1 is also poor at visual representation, and it is difficult to grasp the degree of dysphagia clinically.
In the method disclosed in non-patent article 1, four pressure sensors are disposed on a sensor box at 8 mm intervals, and the sensor box on which the pressure sensors are disposed is fixed to the neck of a subject by a magic tape (registered trademark) for measuring swallowing movement. However, the four pressure sensors disposed apart from each other are not enough to monitor a series of up and down movements of the thyroid cartilage, and the method only has an accuracy of obtaining the time it takes for a patient to complete the swallowing movement. Furthermore, the method also has a disadvantage that the magic tape has to be wound around the neck of a patent, which is uncomfortable for the patient. Moreover, non-patent article 1 and JP Unexamined Patent Publication (Kokai) No. 2006-95264 does not disclose techniques of comparing the waveforms of each kind of data, directly determining the degree of dysphagia based on the waveforms of each kind of data, and determining the degree of dysphagia easily. Thus, the methods disclosed in non-patent article 1 and JP Unexamined Patent Publication (Kokai) No. 2006-95264 are also poor at visual representation, and it is difficult to grasp the degree of dysphagia clinically.
JP Unexamined Patent Publication (Kokai) No. 2005-304890, JP Unexamined Patent Publication (Kokai) No. 2006-95264 and non-patent article 1 disclose an electromyogram as a basic method for measuring the swallowing movement. However, indifferent electrodes or earth electrodes are necessary in a method using an electromyogram as disclosed in non-patent article 1, which increase the number of electrodes, making it troublesome to manage the electrodes.
Furthermore, in a method using an electromyogram, test results may be different unless electrodes are disposed on accurate positions of the laryngeal part because the laryngeal part includes mainly four kinds of muscles (geniohyoid muscle, thyrohyoideus muscle, sternohyoideus and sternothyroideus) as described in JP Unexamined Patent Publication (Kokai) No. 2005-304890. This problem is inevitable as long as an electromyogram is used. In a method which uses an electromyogram, when a patient himself or an untrained nurse measures swallowing, it is difficult for them to position the electrodes accurately and manage them properly. Moreover, when disposable electrodes are used, there is also a problem that the cost of the disposable electrodes is high.
JP Unexamined Patent Publication (Kokai) No. 9-248282 discloses a method in which two acceleration sensors are attached to a band shaped elastic body, and the two acceleration sensors detect vibration in the throat. An object of this method is to detect an audio signal, pulsation signal or the like. In this method, a swallowing sound is mainly detected, but a detected signal is affected a little by the movement of the laryngeal part and it is difficult to separate these signals, and thus the method is not suitable for evaluating dysphagia.
Non-Patent Article 1: “Shohei FUJITA, Ai MURAYAMA, Toyohiko HAYASHI, Yasuo NAKAMURA, Hidetoshi KOJIMA and Noboru MICHIMI, Analysis of Beer Drinking Motion using Swallowing function evaluation system SFN-1, IEICE Technical Report MBE2006-7(2006-5), p. 25-28,
As describe above, because apparatuses used in the VF method and the VE method are large and require a user to be skilled, everybody is not allowed to use the apparatuses to measure swallowing at bed side. The methods disclosed in JP Unexamined Patent Publication (Kokai) No. 2005-304890, JP Unexamined Patent Publication (Kokai) No. 2006-95264 and non-patent article 1 have problems of positioning or managing of electrodes because the methods use an electromyogram, which restricts those who can use these methods. Further, JP Unexamined Patent Publication (Kokai) No. 2005-304890 and non-patent article 1 disclose the methods in which measured data of each kind is analyzed independently, and do not disclose a method for analyzing various kinds of data as a whole or a method for displaying the result of the analysis of the various kinds of data.